Diesel starting fluid



Patented Nov. 20, 1951 DIESEL STARTING FLUID Hebert D. Young, Harvey,11]., assignor to Sinclair Refining Company, New York, N. Y., acorporation oi Maine No Drawing. Application March 31, 1949, Serial No.84,738

2 Claims. 1

This invention relates to the cold weather starting ofcompression-ignition engines, and provides improved. methods and newstarting fluids for cold weather ignition. In one aspect the inventionprovides an improved diesel cold weather starting fluid comprising apredominately saturated, generally parailinic, low pour point, lightpetroleum fraction boiling in the approximate range of 100 to 350 F. inadmixture with diethyl ether. In another aspect the invention provides astarting fluid as described above which has been contacted with oxygenprior to ignition for even greater effectiveness.

In the normal operation of compression-ignition engines, that is, dieselengines, the fuel is ignited by the temperature prevailing in theworking cylinder as the fuel is injected. In starting a cold engine,however, temperatures suflicient to ignite the regular fuel are attainedonly after sufiicient work has been done in the compression of thecharge admitted to the working cylinder so as to bring the parts of theengine in a direct heat exchanging relationship with the contents of theworking cylinder, as well as elevating the charge undergoing compressionto a relatively high temperature. It the atmospheric temperature isbetween about 60 and 80 F., this can be accomplished with a minimum ofdifliculty and without imposing too much of a load on the startingmechanism. However, if the atmospheric temperature falls, the diflicultyof starting a compression-ignition engine increases at an acceleratedrate and becomes almost impossible at temperatures much below F.

To overcome this diiliculty, special auxiliary starting fuels, capableof ignition at relatively low temperatures, are advantageously used.Conventionally, such special auxiliary starting fuels are injected intothe working cylinder of the engine, usually at a point as close to theadmission valve of the cylinder as is practicable in the particularengine. Diethyl ether is one of the best of these auxiliary startingfuels. However, diethyl ether suffers several disadvantages; it isexpensive, volatile, highly inflammable, and frequently explosive.

I have now discovered, however, that readily available mixtures of lighthydrocarbons, particularly those of a relatively narrow boiling rangehaving an initial boiling point considerably above the boiling point ofdiethyl ether, a low pour point, derived from the fractionation ofnaphthas and light petroleum fractions, possess unusual capacity incombination with a relatively minor proportion of diethyl ether forpromoting cold weather starting of c: myres qion-ignition engine's.Moreover, I have discovered that mixtures of such light hydrocarbonswith'diethyl ether possess a surprising susceptibility to the action ofoxygen which upon extended contact or pressurization, promotes oraccentuates their valuable cold weather starting capacities.

The cold weather compression-ignition starting fluid of my invention isa predominately saturated, generally paraiilnic, low pour point, lightpetroleum fraction boiling in the approximate range of to 350 inadmixture with diethyl ether. The startiig fluid mosadvantageouslycomprises mixtures by volume of about 85 to 50% of the light parailimcpetroleum fraction and about 15 to 50% of diethyl ether.

My invention also inc'iudes the related discovery that when fluids as Ihave described are contacted with oxygen prior to ignition an evengreater improvement in starting results. This contact may beadvantageously accomplished by allowing the starting fluid to stand foran extended period of time in contact with air under normal atmosphericconditions, i. e., the liquid may be weathered" in an open container fora period exceeding, say, ten or twenty days and for as long as three orfour months. More practically, however, the liquid is simply confined ina closed container and subjected to superatmospheric air pressure, forinstance, 100 p. s. 1. Or the starting fluid may be injected into theworking cylinder in a stream of an oxygen-containing gas. This ispreferably accomplished by atomizing the liquid into a stream of airleading to the working cylinder where it is ignited.

As illustrative of the predominately paraffinic, low pour point, lightpetroleum fractions used in admixture with diethyl ether are thosefractions comprising substantially normal nonane and the lighter normalparaflins. In particular, I recommend a fraction composed mainly of oneor more of the normal paraflins, heptane, octane, and decane.

Although my invention is not predicated upon any particular hypothesis,it is my belief that the starting effectiveness of diethyl ether is due,not so much to its high volatility, but to its instability under thesevere tempertaures and pressures encountered in a compression-ignitionengine working cylinder. As a result, this may be why petroleumfractions containing thermally unstable, straight chain paraflins reactsomewhat similarly and therefore have value in starting diesel engines.In addition, I believe that the formation of peroxides may be anintermediate step in the conversion of such fluids into highly explosivecompounds within the engine cylinder prior to ignition, which isapparently why the eifectiveness of a starting fluid composition, inaccordance with the preceding definition, is increased upon contact withoxygen prior to ignition. Under these conditions relatively minutequantities of peroxides then may be formed, serving to accelerate therate at which the starting fluid reaches the explosive stage inside thecylinder. And this even though the peroxides may be relatively stableunder normal conditions of temperature and pressure.

The principles of my invention are well illustrated by the followingexamples of engine tests under controlled conditions. A four cylindermarine diesel engine was placed in a laboratory "cold room" and testedwith different starting fluids and procedures. The engine was cranked bya battery-operated starting motor. In the examples the engine and fluidswere chilled for about eight hours to a given temperature. At thistemperature, the engine was cranked for a period not exceeding oneminute, and if the particular fluid used failed to start it in thatperiod after several attempts, the fluid was designated asunsatisfactory for the temperature. As a result, the cold-roomtemperature was then elevated until the engine started satisfactorily. A"start was defined as a firing followed by sustained running of theengine under its own power; spasmodic firing did not constitute a start.

Example I A commercial grade diesel fuel cut back with 20% kerosene wasused for starting without a special starting fuel or procedure. Thediesel fluid had the following characteristics:

Cetane number 52.0 Gravity, A. P. I 40.3 Pour point, F Initial boilingpoint, F 356 10% off at, F 409 50% of! at, F 471 90% ofi at, "F 575 Endpoint, F 655 The diesel engine failed to start at temperatures belowabout plus 40 F.

Example 11 A relatively low boiling solvent naphtha was used as astarting fluid, having the following characteristics:

Cetane number 25.1 Gravity, A. P. I 57.3 Aniline point, F 130 Initialboiling point, F 188 10% off at, F 204 50% off at, F 218 90% ofi at, F24'? End point, F 267 A mechanically-operated pump, or primer," was usedto inject the fluid for starting. The mechanical primer was essentiallya hand-operated piston located within a cylinder containing the startingfluid, to which was attached a nozzle so as to atomize the liquid intothe air intake line leading to the working cylinder. The diesel enginefailed to start at temperatures below about plus 40 F. using the solventnaphtha. A mixture by volume of 80% of the solvent naphtha and 20% ofdiethyl ether was then use as a starting fluid in the mechanical primer.The mixture had the following characteristics:

The diesel engine started at a minimum temperature of about minus 6 F.,at a battery voltage of 12 and a cranking speed of 180 R. P. M., infifty seconds, with 42 cc. of this mixture being injected. There was amedium detonation, while the combustion continuity was good.

Example III A predominantly C7 straight run naphtha cut was used as astarting fluid in the mechanical primer, of the followingcharacteristics:

Cetane number 51.0 Gravity, A. P. I 74.2 Initial boiling point, F 20710% off at, F 208 50% oif at, F 208 off at, F 208 End point, F 228 Thediesel engine started at a minimum temperature of about plus 5 F. Amixture by volume of 80% of the C7 straight run naphtha cut and 20% ofdiethyl ether was then used as a starting fluid in the mechanicalprimer. The mixture had the following characteristics:

Cetane number 51.6 Gravity, A. P. I 72.4 Reid vapor pressure 5.4 Pourpoint, F below 80 Initial boiling point, F 10% oif at, F 154 50% on at,F 204 90% off at, F 208 End point, F 1- 232 The diesel engine started ata minimum temperature of about minus 11 F., at a battery voltage of 12and a cranking speed of R. P. M., in twelve seconds, with 12 cc. of thismixture being injected. There was a medium detonation, while thecombustion continuity was good.

This starting fluid compared very favorably with, for instance acommercial starting fuel which is basically an ethyl ether composition,containing over 85 per cent by volume of ethyl ether with a balance oflubricating oil. Used in the mechanical primer as describedhereinbefore, the commercial starting fuel started with a more severedetonation, followed by a noticeably poorer combustion continuity afterfiring was initiated. Employing the commercial starting fuel, the dieselengine started at a minimum temperature of about minus 2 F., at abattery voltage of 12 and a cranking speed of 180 R. P. M., in fourseconds, with 48 cc. of this fuel being injected.

At a starter battery voltage of 18 and a cranking speed of 180 R. P. M.,this C7-rich mixture started the diesel engine at a minimum temperatureof about minus 14 F., with 18 cc. of the fluid being injected.

At a starter battery voltage of 24 and a cranking speed of 200 R. P. M.,this C1-rich mixture started the diesel engine at a minimum temperature01' about minus 18 F., with 18 cc. of the fluid being injected.

Example IV A starting fluid comprising a mixture by volume of 80% of a(Iv-rich naphtha out similar to that of Example III and 20% of diethylether was contacted with oxygen at an elevated pressure, by containingthe'liquid in a six-ounce "pressurized bomb" under 100 p. s. i. of airpressure. The bomb was equipped with a valve and air hose connection atthe exit end and so located on the diesel engine as to deliver theoxygencontaining fluid into the intake line of the working cylinder.

At a starter battery voltage of 12 and a cranking speed o! 150 R. P.11., use bomb-injected mixture started the engine at a minimumtemperature of about minus 9 F. in two seconds. There was a mediumdetonation, while the combustion continuity was good.

At a starter battery voltage of 24 and a cranking speed of 140 R. P. M.,this bomb-injected mixture started the engine at a minimum temperature01 about minus 25 1''.

Example V A starting fluid comprising a mixture by volume of 80% 01 aCa-rich naphtha out similar to that oi. Example 111 and 20% of diethylether was contacted with oxygen for a prolonged period of time prior toignition. The mixture was allowed to stand in the air for ninety days inan open, clear glass container exposed to natural light. Over aforty-tour day period, the loss or liquid through evaporation amountedto about 20%. the loss including both the dietlnvi ether and 100 p. s.i. of air pressure as described in Example IV.

At a starter battery voltage of 12 and a cranking speed of 150 R. P. M.,this bomb-injected mixture started the engine at a minimum temperatureof about minus 8 F., in two seconds. There was a medium detonation,while the combustion continuity was good.

Example VII A mixture by volume of 80% of a predominately 010 straightrun naphtha cut in admixture with 20% of diethyl ether was used as astarting fluid, having a cetane number over 70, an A. P. I. gravity of613 and a pour point or minus 21.5 F. The mixture was contacted withoxygen at an elevated pressure by containing the fluid in a six-ouncepressurized bomb" under 100 p. s. i. 0! air pressure as described inExample IV.

At a starter battery voltage of 12 and a cranking speed of 150 R. P. M.,this bomb-imected mixture started the engine at a minimum temperature ofabout minus 9 F., in two seconds. There was a medium detonation, whilethe combustion continuity wa good.

(Jr-rich naphtha cut. During a iorty-iour day period, the peroxidecontent increased from 0 to 2.1 mg.

Using this weathered" fluid in the mechanical primer, the diesel enginestarted at a minimum temperature of about minus 17 F., at a batteryvoltage of 12 and a cranking speed or 180 R. P. M. in two seconds, with3 cc. of this mixture being inJected. There was a moderate detongotilon.while the combustion continuity was I ammle Vi A. P. I. gravity of 683and a pourpoint 0! minus 702 F. The mixture was contacted with oxygen atan elevated pressure by containing the fluid in a six-ounce "pressurisedbomb" under I claim: I

1. A starting fluid for compression-ignition engines containing about15. to 50 per cent by volume of diethyl ether and to 50 per cent of apredominantly straight chain parafllnic, low

pour point, light close out petroleum traction boiling within theapproximate range of to 350 F- selected from the group consisting ofnormal C1, Cs. Cs and Cm cuts.

2. A starting fluid for compression ignition engines containing about15%-50% by volume diethyl ether and 85%-50% of normal heptane.

HOBERT D. YOUNG.

REFERENCES CITED The following references are of record in the flle ofthis patent:

Cloud et al., Sp cial Cold-Starting Fuels for Diesel Engines," 8. A. E.Journal, vol. 52, pp. 223-227, June 1944.

1. A STARTING FLUID FOR COMPRESSION-IGNITION ENGINES CONTAINING ABOUT 15TO 50 PER CENT BY VOLUME OF DIETHYL ETHER AND 85 TO 50 PER CENT OF APREDOMINANTLY STRAIGHT CHAIN PARAFFINIC, LOW POUR POINT, LIGHT CLOSE CUTPETROLEUM FRACTION BOILING WITHIN THE APPROXIMATE RANGE OF 100* TO 350*F. SELECTED FROM THE GROUP CONSISTING OF NORMAL C7, C8, C9 AND C10 CUTS.